What does double-time cadence refer to in marching?

Double-time cadence in marching specifically refers to the pace of 180 thirty-inch steps per minute. This level of activity is significantly faster than regular marching and is typically used in military formations when speed is essential. The measurement of "thirty-inch steps" indicates the length of each step taken, which is a standard measurement in military marching.

Understanding double-time cadence is crucial for maintaining coordination and synchronization within troops when rapid movement is required. The other options represent either inconsistent or incorrect stepping rates for double-time marching, making option "C" the only accurate representation of this marching cadence.